Air management systems including Heating, Ventilation and Air-Conditioning (“HVAC”) are common in modern enclosed spaces, such as inter alia a building, vehicle or vessel. One of the goals of HVAC systems is to provide a comfortable and healthy environment for the enclosed space occupants, in terms of temperature, humidity, composition and cleanliness of the indoor air. Additionally, HVAC systems allow control of the substance concentration for maintaining the indoor air at a desired degree, thereby ensuring good air quality.
Air management systems typically comprise Air Handling Units (AHU). The AHU supplies conditioned air to various locations in the enclosed space, using fans and dampers to manage airflow while bringing the air into contact with coils, screens, and other media. Some air handling systems are supplied with chilled or warmed fluid from a separate, possibly remote chiller or heater, whereas some air handling units or handlers are integrated with a dedicated chiller or heater; the latter are sometimes referred to as “packaged units” (PU). In most HVAC installations, air circulates in the enclosed space, in other words conditioned air (“supply air”, or SA) is delivered to the enclosed space from one or more AHUs, typically through a network of ducts or conduits, and indoor, return air (RA) also flows back from the enclosed space to the AHU through separate ducts or channels, where it is reconditioned and circulate back to the enclosed space.
Indoor air within and around enclosed spaces is affected by a plurality of substances, comprising contaminants or pollutants. Among these contaminants are gaseous contaminants, such as carbon dioxide (CO2), carbon monoxide, nitrous oxides, sulfur oxides and radon and other inorganic gases as well as a broad class of organic gases and vapors, referred to as Volatile Organic Compounds (VOCs). Particles and microorganisms also represent non-gaseous contaminants that affect indoor air quality and should be filtered or removed. These contaminants are often generated inside the building by its occupants, systems and content. In order to maintain good air quality, HVAC systems are typically configured to replace indoor air with outdoor air or, alternatively, to allow the air to flow through air scrubbers. Outdoor air may be air from out of the enclosed space.